Expression of thrombospondin 1 on the surface of activated platelets mediates their interaction with the heavy chains of human kininogens through Lys 244-Pro 254.
Platelet thrombospondin (TSP1) forms a complex with high (HK) and low (LK) molecular weight kininogens. We isolated a proteolytic fragment from HK and LK heavy chains (12 kDa) recognized by TSP1 with a N-terminal sequence, K244ICVGCPRDIP254. Lys244-Pro254 oxidized to cyclic form prevented binding of 125I-LK to TSP1. This effect was abolished by reduction and alkylation. Oxidized peptide KICVGCPRDIP (100 microM) reversed the known inhibitory effects of LK or HK (1 microM), on thrombin-induced platelet activation, suggesting this peptide forms part of the cell binding site on HK and LK for activated platelets. KICVGCPRDIP completely inhibited the binding of 125I-LK to activated platelets. However, the peptide only partially inhibited binding of 125I-HK to platelets, suggesting an additional binding site on the HK light chain. Fluorescein-labeled KICVGCPRDIP bound directly and specifically to activated platelets. A monoclonal antibody directed to TSP1 partially inhibited the binding of 125I-HK to activated but not inactivated platelets. We conclude residues Lys244-Pro254 on kininogen heavy chain is responsible for binding to thrombospondin on the surface of activated platelets.
DeLa Cadena
R A
RA
Sol Sherry Thrombosis Research Center, and Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Kunapuli
S P
SP
Walz
D A
DA
Colman
R W
RW
D000595:Amino Acid Sequence; D001710:Biotin; D006801:Humans; D016285:Iloprost / Q000494:pharmacology; D007704:Kininogens / Q000097:blood*; D008239:Lysine; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000097:blood*; D015539:Platelet Activation; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011392:Proline; D017434:Protein Structure, Tertiary; D013499:Surface Properties; D019699:Thrombospondins / Q000097:blood*
D007704:Kininogens; D010446:Peptide Fragments; D010975:Platelet Aggregation Inhibitors; D019699:Thrombospondins; D001710:Biotin; D011392:Proline; D016285:Iloprost; D008239:Lysine